onto a vertical plane until it resembles the angle in which the said object is to be represented.
528.
Why are paintings seen more correctly in a mirror than out of it?
529.
HOW THE MIRROR IS THE MASTER [AND GUIDE] OF PAINTERS.
When you want to see if your picture corresponds throughout with the objects you have drawn from nature, take a mirror and look in that at the reflection of the real things, and compare the reflected image with your picture, and consider whether the subject of the two images duly corresponds in both, particularly studying the mirror. You should take the mirror for your guide—that is to say a flat mirror—because on its surface the objects appear in many respects as in a painting. Thus you see, in a painting done on a flat surface, objects which appear in relief, and in the mirror—also a flat surface—they look the